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层状前体镁铁水滑石及磁性材料的制备及表征 总被引:4,自引:0,他引:4
本文提出了利用镁铁水滑石作为磁性材料前体再经高温焙烧制备尖晶石型铁氧体的思路,深入研究了水滑石的制备工艺及结构性能并初步探讨了其焙烧后的磁学性能。由共沉淀法合成了Mg/Fe摩尔比为2,3,4,6的镁铁水滑石,XRD结果表明随镁铁比增大、晶化温度的升高及晶化时间的延长,水滑石的晶体结构规整性增强;热重-差热结果显示镁铁水滑石的分解有两个过程,随着镁铁比增大,水滑石的热稳定性提高。高温焙烧后的镁铁水滑石具有较好的磁学性能。 相似文献
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控制铝酸钠溶液中硅的含量在氧化铝工业中是非常重要的.本文以制碱工业中的副产物氯化钙为原料合成了两种Ca-Al水滑石,Friedel盐和Kuzel盐,并以合成的两种盐为脱硅剂对铝酸钠溶液的脱硅进行了研究.考察了脱硅温度、脱硅时间、苛性比(铝酸钠溶液中Na2O与Al2O3的摩尔数比)、铝酸钠溶液浓度、初始硅量指数(铝酸钠溶液中Al2O3与SiO2的质量比)及Ca-Al水滑石的添加量对脱硅效果的影响,并对Ca-Al水滑石与CaO的脱硅效果进行了比较.实验结果表明用Ca-Al水滑石作为脱硅剂时,可使硅量指数由75提高到600以上.Ca-Al水滑石的脱硅效果优于CaO,而Kuzel盐优于Friedel盐.动力学结果表明Friedel盐脱硅反应对SiO2的浓度是一级反应,表观活化能为17.3kJ/mol.通过XRD对脱硅产物进行了分析,并探讨了Ca-Al水滑石的脱硅机理. 相似文献
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含钴铜镍类水滑石焙烧产物催化分解N2O的研究 总被引:2,自引:0,他引:2
合成了含Co,Cu和Ni的M/Mg-Al-HTL类水滑石,并将其焙烧产物用于N2O催化分解反应.实验结果表明,Co/Mg-Al-HTL对N2O分解反应的催化活性明显高于Cu/Mg-Al-HTL和Ni/Mg-Al-HTL的活性.在保持样品中Al含量不变的条件下,催化活性随着Co含量的增加及Mg含量的减少而升高,各催化剂的活性顺序为:Co/Al-HTL>Co/Mg-Al-HTL>Cu/Mg-Al-HTL>Ni/Mg-Al-HTL.在此基础上,进一步考察了Co/Al-HTL中Co/Al原子比调变对催化剂活性的影响.对含Co类水滑石及其焙烧产物进行了XRF,XRD和N2O-TPD表征.结果表明,含Co类水滑石具有典型的水滑石结构,其高温焙烧产物都含尖晶石相.由于尖晶石相中Co-O-Al活性中心的作用,含Co类水滑石对N2O分解反应表现出较高的催化活性.随着Co/Al原子比的增大,含Co类水滑石焙烧产物的尖晶石相特征更加突出,Co-O-Al活性中心数目随之增多,催化剂的活性也相应升高. 相似文献
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层状前体镍铁水滑石及磁性材料的制备及表征 总被引:2,自引:0,他引:2
提出了利用镍铁水滑石作为磁性前体再经高温焙制备尖晶石型铁氧体思路,深 入研究了水滑石的制备工艺及结构性能并初步探讨了其焙烧后的磁学性能。由共沉 淀法合成了Ni/Fe摩尔比为2,3,4,6的镍铁水滑石,XRD结果表明镍铁比为3时晶 形较为理想,且随着晶化温度的升高及晶化时间的延长,水滑石的晶体结构规整性 增强。热重-差热结果显示镍铁水滑石的分解有两个过程,当镍铁比为3时,水滑石 的热稳定性相对最高。高温焙烧后的镍铁水滑石具有磁性。 相似文献
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以MgAl-CO3型水滑石为前体,由离子交换法进行插层组装,合成了EDTA柱撑的MgAl-EDTA水滑石,并用X射线衍射、红外光谱对样品进行了表征。探讨了n(Mg)/n(Al)摩尔比、pH、反应温度、EDTA与前体水滑石配比对插层反应的影响,结果表明,当n(Mg)/n(Al)摩尔比为2~3、pH在4.5左右、反应温度控制在150℃以上、同时保证过量的EDTA时,EDTA可以插入MgAl-CO3水滑石层间,取代CO23-,形成结构完好的EDTA柱撑水滑石。MgAl-EDTA柱撑水滑石通过层间EDTA对Cu2+的螯合作用,可以在较短的时间内吸附溶液中的Cu2+,溶液中Cu2+的去除率在96%以上。 相似文献
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层状化合物镍铝水滑石的制备和表征 总被引:14,自引:0,他引:14
采用变化pH值法和恒定pH值法 ,以硝酸镍、硝酸铝为原料 ,NaOH为沉淀剂水热合成了层状化合物镍铝水滑石。分别测定了Ni/Al摩尔比为0 5、1 0、2 0、6 0和10 0混合金属盐溶液的NaOH滴定曲线 ,并利用XRD对滴定过程中不同pH值阶段的合成物进行物相鉴定。实验结果表明 ,在Ni/Al=1 0~6 0范围内 ,不论起始混合盐溶液中Ni/Al摩尔比如何 ,在pH=5.0~6 .0范围内 ,均能合成结构单一的镍铝水滑石 ,随Ni/Al比的增加 ,合成的HTLc(水滑石)中镍含量随之增加 ;合成体系在较低pH(3 3~4 .8)范围为Al(OH) 3 生成阶段 ,较高pH(6.0~7 .5)范围为Ni(OH) 2 和HTLc 的共生阶段。该研究同时考察了其它因素在合成过程中的影响 ,筛选出镍铝水滑石合成的最佳条件。 相似文献
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PiaoPingYANG JianFengYU TongHaoWU GuoZongLIU TaeSunCHANG DongKooLEE DeugHeeCHO 《中国化学快报》2004,15(1):90-92
The urea decomposition property at high temperature has been used to control the pH value in the synthesis of layer compounds. The hydrotalcites of Mg-Al and Ni-Al with high crystallinity were synthesized by using this property. 相似文献
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J. Theo Kloprogge Leisel Hickey Ray L. Frost 《Journal of solid state chemistry》2004,177(11):4047-4057
Zn/Al hydrotalcites were synthesized by coprecipitation at increasing pH from 6.0 to 14.0, followed by hydrothermal treatment at 150 °C for 7 days. The materials were characterized by X-ray diffraction (XRD), STEM, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), thermal analysis, infrared spectroscopy and Raman spectroscopy. The XRD analysis for the samples prepared between pH 9.0 and 12.0 showed a pattern typical of hydrotalcite, with a c-axis distance of ∼22.6 Å. STEM showed that the pH of preparation affected the stability of the hydrotalcite and that instability, observed at pH 9.0, favored the formation of mixed phases when treated hydrothermally. It was also shown that treatment of a stable starting material increased the crystallinity and resulted in the formation of hexagonal plate-shaped particles. ICP-AES and thermal analysis showed that the Zn/Al ratio and thermal stability increased with pH. Thermal analysis showed three major weight losses corresponding to the loss of interparticle water, interlayer water and dehydroxylation of the hydroxide layers and decarbonization of the interlayer region. 相似文献
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Ralla K Sohling U Suck K Sander F Kasper C Ruf F Scheper T 《Colloids and surfaces. B, Biointerfaces》2011,87(2):217-225
In this study, the potential use of a synthetic Mg/Al hydrotalcite (layered double hydroxide) as a novel chromatography material for protein purification was investigated. The hydrotalcite is present in its carbonate form and is characterized by an Al/Mg-ratio of 1.85. Zetapotential measurements confirm a positive surface potential up to pH 10 suggesting applicability as anion exchanger. The binding of model proteins covering a broad range of isoelectric points and molecular weights was performed at different pH-values under batch conditions to evaluate the binding behaviour of the hydrotalcite. Furthermore, static binding capacities were exemplarily determined for hemoglobin and human serum albumin. Additionally, the adsorption and elution of hemoglobin was studied under dynamic conditions. The binding behaviour of the hydrotalcite was compared to commercially available anion exchangers and was found to be a function of pH, depending on the model protein. Variant adsorption behaviour is explained by further interactions like hydrogen bonds and by an unequal charge distribution over the protein surfaces. The hydrotalcite reveals high adsorption capacities under static (260 mg/g) as well as under dynamic conditions (88 mg/g at 34 cm/h; 61 mg/g at 340 cm/h). With appropriate buffers like 500 mM carbonate (pH 10) the adsorbed proteins can be nearly completely desorbed making regeneration possible. Due to the binding and elution properties it is concluded, that the hydrotalcite can serve anion exchange material for chromatographic protein separations. 相似文献
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Layered double hydroxides (LDHs) exhibit characteristic anion-exchange chemistry making them ideal carriers of negatively charged molecules like deoxyribonucleic acid (DNA). In this study, hydrotalcite (Mg−Al) and hydrotalcite-like compounds (Mg−Fe, Zn−Al, and Zn−Fe), also known as LDHs, were evaluated for their potential application as a carrier of DNA. LDHs were prepared by coprecipitation at low supersaturation and characterized by Powder X-ray diffraction (XRD), infrared (IR), Raman, and inductively coupled plasma—optical emission spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD patterns showed strong and sharp diffraction peaks for the (003) and (006) planes indicating well-ordered crystalline materials. TEM images yielded irregular circular to hexagonal-shaped particles of 50–250 nm in size. Varying degrees of DNA binding was observed for all the compounds, and nuclease digestion studies revealed that the LDHs afford some degree of protection to the bound DNA. Minimal toxicity was observed in human embryonic kidney (HEK293), cervical cancer (HeLa) and hepatocellular carcinoma (HepG2) cell lines with most showing a cell viability in excess of 80 %. All LDH complexes promoted significant levels of luciferase gene expression, with the DNA:Mg−Al LDHs proving to be the most efficient in all cell lines. 相似文献